1. Field of the Invention
The present invention relates to a recording apparatus including a carriage having a recording head thereon and reciprocably moving over a recording medium in the main-scanning direction and a recording medium conveying unit being capable of conveying the recording medium in the sub-scanning direction, a recording control computer readable medium storing thereon program for the recording apparatus, and a recording method.
Cross Reference to Related Application: The present application claims priority from Japanese Patent Applications No. 2006-008708 filed on Jan. 17, 2006 and No. 2007-003288filed on Jan. 11, 2007, the contents of which are incorporated herein by reference.
2. Related Art
A recording apparatus including a carriage having a recording head thereon and reciprocably moving over a recording medium in the main-scanning direction and a recording medium conveying unit being capable of conveying the recording medium in the sub-scanning direction has been known as for example, in Japanese Patent Application Publication No. 2005-74968. The carriage of the recording apparatus includes thereon a sensor that detects the end of a recording medium out of contact therewith, which is called as a PW sensor, a PW detector and a paper width sensor (hereinafter referred to as “PW sensor”). In the recording apparatus, the PW sensor scans a recording medium to detect the position of the end of the recording medium in the main-scanning direction when the carriage reciprocates to the main-scanning direction. The recording apparatus specifies the witch of the recording medium in the main-scanning direction based on the end position in the main-scanning direction and determines the width in the main-scanning direction, i.e. the width of the region in, which dots are formed in the main-scanning direction, of a region in which liquid is ejected onto the recording medium based on the specified width of the recording medium in the main-scanning direction.
Additionally, in order to control to record on the recording medium, it is necessary to also specify the start position and the end position of a region in which dots are formed in the sub-scanning direction in addition to the width of the region in which dots are formed in the main-scanning direction. Therefore, the recording apparatus having the PW sensor could utilize the PW sensor in order to detect the front edge position and the rear edge position of the recording medium in being recorded (the front edge position and the rear edge position in the sub-scanning direction). For example, when the recording medium is conveyed to the recording start position at the time at which a recording is started, the front edge of the recording medium is detected by the PW sensor, so that the front edge of the recording medium in a conveying path can be detected and conveyed to the start position of the dot forming region.
Meanwhile, if the recording medium is scanned for each main-scanning in recording and it is detected whether there is any recording medium, it can be specified that the rear edge of the recording medium in being recorded passes from the PW sensor to the downstream side in the sub-scanning direction. That is to say, the position of the recording medium in the conveying path, which is detected by the PW sensor in main-scanning is determined as the rear edge position of the recording medium in the conveying path, and the rear edge position is determined as the end position of the dot forming region, so that a control to mask dot formation in the region behind the end position (the upstream side of the sub-scanning direction) can be performed.
However, in order to perform the control to mask the dot formation in the region behind the recording medium after the rear edge of the recording medium in being recorded is detected by the PW sensor as described above, the rear edge of the recording medium should be disposed upstream than the recording head for forming dots in the sub-scanning direction Otherwise, the dots could be formed in a region behind the rear edge of the recording medium before the rear edge of the recording medium is detected by the PW sensor. Therefore, there has been a restriction on the carriage that the PW sensor has to be disposed on the upstream side in the sub-scanning direction at more than certain distance from the recording head for forming dots.
Additionally, the position of the rear edge of the recording medium in being recorded, which is specified as described above is varied within the amount of conveyance in main-scanning, so that any error up to the amount of conveyance could be generated. Therefore, there has been a problem that a control to mask the dot formation in the region behind the position of the rear edge of the recording medium in being recorded can not be accurately performed.
Still more, it can be considered that a sensor that detects the rear edge of the recording medium is newly provided on a region upstream than the recording head in the sub-scanning direction instead of the PW sensor, and a mask control is started after it is detected that the rear edge is conveyed by the sensor and then the recording medium is conveyed by a certain distance. However, in this case, there has been a problem for unit for conveying the recording medium that it becomes different between the predetermined certain distance and an actual distance from the position of the rear edge to the recording head detected by the sensor along with the change over time.
Thus, the advantage of the present invention is to provide a recording apparatus being capable of accurately specifying the rear edge of a recording medium in being recorded to accurately perform a control to mask dot formation in the region behind the rear edge of the recording medium in being recorded.